1. Field of the Invention
The present invention relates to an image-forming device such as a laser printer, and a developer cartridge detachably mounted in the image-forming device.
2. Description of Related Art
In conventional laser printers, developer cartridges accommodating toner are detachably mounted therein. This type of laser printer is provided with new product detecting means for detecting whether the developer cartridge mounted in the laser printer is a new product and for determining the life of the developer cartridge from the point that the new product was detected.
For example, Japanese unexamined patent application publication No. 2000-221781proposes a developing device in which is provided a sector gear having a recessed part and a protruding part. When a new developing device is mounted in the body of an electrophotographic image-forming device, the protruding part formed on the sector gear is inserted into a new product side sensor, turning the new product side sensor on. After the developing device has been mounted in the body of the image-forming device, an idler gear is driven to rotate. When the idler gear begins to rotate, the sector gear also rotates, moving the protruding part from the new product side sensor to an old product side sensor. The protruding part is inserted into the old product side sensor, turning the old product side sensor on. At the same time, the idler gear arrives at the recessed part of the sector gear, and the sector gear stops rotating.
However, some users have requested the freedom to select an optimum developer cartridge from a plurality of developer cartridges in different price ranges corresponding to the amount toner accommodated therein with consideration for cost and frequency of use. To meet this demand, developer cartridges accommodating different amounts of toner must be provided. However, the toner accommodated in these developer cartridges has different agitation properties and different rates of degradation based on the amount of toner.
Under these circumstances, it is not sufficient merely to detect whether the developer cartridge is a new product since the life of the developer cartridge from this point of detection may differ according to the amount of toner accommodated therein. Accordingly, the life of the developer cartridge cannot be accurately determined. As a result, a developer cartridge accommodating a small amount of toner may actually reach the end of its life before such a determination is made, resulting in a decline in image quality.